Abstract: Attack angle is a key index to evaluate the stability of snakelike motion in the train. Due to the complexity of the running train and the small angle of attack, it is difficult to measure the angle between the wheel and rail. This paper presents a method for attack angle detection based on the laser line and the direction of motion as collinear wheel on the rail surface. The laser line and orbital edge line were obtained by image correction, Meanshift smoothing, and Radon line detection, and then the angle was calculated in the image. Comparison between simulation data and test results shows that the method can realize the detection of attack angle and it is simple and feasible at the same time. Finally, the correction method of the detection error is given, which increases the stability of the detection method. This method may lay the foundation for the evaluation of stability and safety of train operation.